Method and system for incoming call notification

ABSTRACT

A mobile station that is fully engaged such that it cannot be connected to an incoming call without being disconnected from an existing call receives an incoming call notification. The incoming call notification may, for example, take the form of a short message system (SMS) message or a packet protocol message, such as a session initiation protocol (SIP) message. The incoming call notification may identify the calling party and may explain how to take the incoming call. If the user accepts the incoming call, the mobile station is disconnected from existing calls and connected to the incoming call.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of U.S. patent application Ser.No. 09/708,836, filed Nov. 8, 2000, which application is fullyincorporated herein by reference.

BACKGROUND

[0002] 1. Field of the Invention

[0003] The present invention relates to telecommunications and, moreparticularly, to methods and systems for notifying mobile stations ofincoming calls.

[0004] 2. Description of Related Art

[0005] A wireless service subscriber who has call waiting is able toreceive notification of an incoming call when engaged in a voice call.Typically, the subscriber's mobile station provides an audibleindication of the incoming call and visibly displays an identificationof the calling party. The subscriber is then able to signal the wirelesstelecommunications network, such as by pressing the SEND button on themobile station, to put the first call on hold and connect the incomingcall.

[0006] Existing call waiting services have significant limitations,however. Call waiting is typically not available when a subscriber isalready using call waiting to maintain two calls or when the user isengaged in a three-way call. In particular, because of network and/ormobile station limitations, wireless networks typically limit the numberof call legs that a mobile station can maintain at one time. Thus, whena subscriber is using the maximum number of call legs that the wirelessnetwork allows, the subscriber will typically not receive any indicationif another request to terminate a call to the mobile station comes in.

[0007] Call waiting may also be unavailable when the mobile station isinvolved in an active data session. For example, the CDMA 2000 3G1xstandard does not support simultaneous voice and data transmission tothe mobile station. As a result, if the mobile station is involved in anactive data session it will not receive any notification of incomingvoice calls. In other implementations, the mobile station may be able tomaintain simultaneous voice calls and active data sessions, albeit up toa maximum number.

[0008] Thus, when a mobile station is fully engaged such that it cannotbe connected to another call without being disconnected from an existingcall (either because it is using all available call legs or because itis involved in an active data session) the mobile station will not benotified of incoming calls. As a result, the user may miss importantcalls when the user's mobile station is fully engaged. Indeed, the usermay not realize that anyone is trying to call him while his mobilestation is fully engaged.

[0009] Accordingly, there is a need to provide an incoming callnotification to mobile stations that are fully engaged.

SUMMARY

[0010] In a first principal aspect, the present invention provides amethod of incoming call notification for a mobile station that isconnected to at least one call over an air interface. In accordance withthe method, a request to connect an incoming call to the mobile stationis detected. A determination is made whether the mobile station is fullyengaged such that it cannot be connected to the incoming call withoutbeing disconnected from at least one of its current calls. If the mobilestation is fully engaged, an incoming call notification is transmittedto the mobile station.

[0011] In a second principal aspect, the present invention provides asystem for notifying a mobile station of an incoming call. The systemcomprises a call connection system for connecting calls to the mobilestation over an air interface, and a call control system for controllingthe call connection system. The call control system runs service logicfor formulating an incoming call notification to the mobile station whenthe mobile station is fully engaged.

[0012] In a third principal aspect, the present invention provides amethod of handling an incoming call for a mobile station that isconnected to at least one call over an air interface. In accordance withthe method, a first attempt to connect an incoming call from a callingparty to the mobile station is made. The first attempt is determined tobe unsuccessful. In response, an incoming call notification istransmitted, and a second attempt to connect the incoming call from thecalling party to the mobile station is made.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a simplified block diagram of a wirelesstelecommunications system, in accordance with an exemplary embodiment ofthe present invention;

[0014]FIG. 2 is a flow chart illustrating an incoming call notificationservice, in accordance with an exemplary embodiment of the presentinvention;

[0015]FIG. 3 is a simplified call flow diagram illustrating an incomingcall notification service, in accordance with an exemplary embodiment ofthe present invention; and

[0016]FIG. 4 is a simplified call flow diagram illustrating an incomingcall notification service, in accordance with an exemplary embodiment ofthe present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0017] 1. Exemplary Architecture

[0018] Referring to the drawings, FIG. 1 is a simplified block diagramof an exemplary wireless telecommunications system 10 in which exemplaryembodiments of the present invention may be employed. In FIG. 1, dottedlines indicate connections that carry primarily signaling traffic, andsolid lines indicates connections that carry bearer traffic, such asvoice, data, or other media.

[0019] Wireless telecommunications system 10 includes a base transceiverstation (BTS) 12 that provides a wireless coverage area within which BTS12 may communicate with one or mobile stations, such as mobile station14, over an air interface. Mobile station 14 may be a wirelesstelephone, a wireless personal digital assistant (PDA), a wirelesslyequipped laptop computer, or other such device. The communicationsbetween BTS 12 and mobile station 14 may occur in a digital format, suchas CDMA, TDMA, or GSM, or they may occur in an analog format, such asAMPS. A preferred wireless communications format is “CDMA 2000,” such asdescribed in EIA/TIA/IS-2000 Series, Rev. A (published March 2000),which is incorporated herein by reference.

[0020] BTS 12 is controlled by a base station controller (BSC) 16,which, in turn, is controlled by a serving mobile switching center (MSC)18. Serving MSC 18 is connected to the public switched telephone network(PSTN) 20. Serving MSC 18 is also able to signal to the home locationregister (HLR) 22 of mobile station 14 and to a service control point(SCP) 24. This signaling may occur via one or more signal transferpoints (STPs), such as STP 26. Although FIG. 1 shows serving MSC 18connected to one BSC and shows BSC 16 connected to one BTS, in general,serving MSC 18 may be connected to more than one BSC and each BSC, suchas BSC 16, may be connected to more than BTS.

[0021] Mobile station 14 is also associated with a home MSC 28.Specifically, mobile station 14 may have a directory number allocated tohome MSC 28, such that calls to that directory number are routed to homeMSC 28. Home MSC 28 is connected to PSTN 20. MSC 28 is also able tosignal HLR 22 and SCP 24, such as via STP 26. For the sake ofsimplicity, home MSC 28 is not shown connected to any BSC in FIG. 1.However, it is to be understood that home MSC 28 may, like serving MSC18, be connected to one or more BSCs, which, in turn, may be connectedto one or more BTSs.

[0022] PSTN 20 is also connected to landline telephones, such astelephone 30, typically via switching systems, such as service switchingpoint (SSP) 32. Although FIG. 1 shows PSTN 20 connected to only two MSCsand one SSP, in general, PSTN 20 is connected to many MSCs and manySSPs. In addition, PSTN 20 may be connected to other types oftelecommunications systems. For example, PSTN 20 may be connected tovarious gateways in order to send calls to or receive calls frompacket-switched networks, such as the Internet. The packet-switchednetworks may carry such calls in a packet-based format, such as a voiceover Internet Protocol (VoIP) format.

[0023] The systems connected to PSTN 20, such as serving MSC 18, homeMSC 28, and SSP 32, may use a signaling system, such as SS7, to routecalls through PSTN 20. The signaling between serving MSC 18, home MSC28, and HLR 22 may conform to IS-41 specifications. A recent revision ofthe IS-41 specifications, ANSI-41 Rev. D, published in July 1997, isincorporated herein by reference. The signaling between serving MSC 18,home MSC 28, and SCP 24 may conform to the specification “WirelessIntelligent Network,” TIA/EIA/IS-771, published in July 1999, which isincorporated herein by reference. Other signaling protocols could beused, however. In this way, serving MSC 18, BSC 16, and BTS 12 mayconnect incoming calls from PSTN 20, which calls may originate fromcalling parties using landline telephones, mobile stations, or othercommunication devices, to mobile station 14. Similarly, serving MSC 18,BSC 16, and BTS may connect calls originating from mobile station 14 totheir destinations, via PSTN 20.

[0024] Mobile station 14 may also be able to access packet-basedservices via a packet-switched network 34, such as the Internet. Suchpacket-based services may include e-mail, wireless web browsing, instantmessaging, and “push-to-talk” teleconferencing, for example. Thesepacket-based services may be provided by one or more application servers36.

[0025] To provide access to packet-switched network 34 and applicationservers 36, BSC 16 may include a packet control function (PCF), and apacket data serving node (PDSN) 38 may connect BSC/PCF 16 topacket-switched network 34. The communications between BSC/PCF 16,serving MSC 18, and PDSN 38 may conform to “third generation” (3G)specifications. Examples of such 3G specifications include “Wireless IPNetwork Standard,” 3GPP2 P.S0001-A, dated Jul. 16, 2001 and “3GPP2Access Network Interfaces Interoperability Specification,” 3GPP2A.S0001-A, dated June 2001, which are incorporated herein by reference.Briefly stated, under these 3G specifications, when mobile station 14requests packet data service, BSC/PCF 16 engages in signaling withserving MSC 18 and with PDSN 38 to authenticate and authorize mobilestation 14 and to set up a data link with PDSN 38. If this process issuccessful, a point-to-point protocol (PPP) session is establishedbetween mobile station 14 and PDSN 38. PDSN 38 may also dynamicallyassign an Internet Protocol (IP) address to mobile station 14.Alternatively, mobile station 14 may use Mobile IP, in which case mobilestation 14 sends a registration request, via PDSN 38, to a home agent40. If home agent 40 approves the registration request, home agent 40may dynamically assign mobile station 14 an IP address, or mobilestation 14 may use an IP address permanently assigned to it. PDSN 38then acts as a network access server, providing mobile station 14 accessto packet-switched network 34.

[0026] PDSN 38 may exchange messages with an authentication,authorization, and accounting (AAA) server 42, such as viapacket-switched network 34. For example, PDSN 38 may query AAA server 42to authenticate and authorize requests by mobile stations, such asmobile station 14, for access to packet-switched network 34. PDSN 38 mayalso send status messages to AAA server 42 when PDSN 38 starts and stopsdelivering packet data services to mobile stations, such as mobilestation 14. The communications between PDSN 38 and AAA server 42 mayconform to the RADIUS protocols specified in “Remote Authentication DialIn User Service (RADIUS),” Request For Comments 2138 (April 1997) and“RADIUS Accounting,” Request For Comments 2139 (April 1997), which areincorporated herein by reference. Alternatively, the communications withAAA server 42 may conform to the DIAMETER protocol specified in Calhoun,et al., “Diameter Base Protocol,” Internet-Draft (June 2002), or to someother protocol.

[0027] In an alternative approach for providing access topacket-switched network 34, serving MSC 18 may be connected topacket-switched network 34 via an interworking function (IWF) 44.Serving MSC 18 and IWF 44 may allow mobile stations, such as mobilestation 14, to access packet-switched network 34 in circuit-switcheddata (CSD) sessions.

[0028] Many other types of servers may also be connected topacket-switched network 34. For example, communications sessions throughpacket-switched network 34 may by initiated using the Session InitiationProtocol (SIP). Accordingly, one or more SIP servers, such as SIP proxyserver 46, may be connected to packet-switched network 34. SCP 24 mayalso be connected to packet-switched network 34 and may use the SIPprotocol for communications via packet-switched network 34. Relevantaspects of SIP are described in J. Rosenberg, et al., “SIP: SessionInitiation Protocol,” Request For Comments 3261 (June 2002) and J.Rosenberg, “Session Initiation Protocol Extensions for InstantMessaging,” Internet Draft (May 3, 2002), which are incorporated hereinby reference.

[0029] A call state server 48 may also be connected to packet-switchednetwork 34. As described in more detail below, call state server 48obtains and maintains information regarding the call state of mobilestations, such as mobile station 14. Such call state information mayinclude the number and types of calls in which the mobile station isengaged.

[0030] 2. Exemplary Operation

[0031]FIG. 2 is a flow chart illustrating, at a high level, the overalloperation of a call notification service in accordance with an exemplaryembodiment. The process begins when the wireless telecommunicationsnetwork detects an incoming call to a mobile station that it is serving,as indicated by block 50. To determine whether it can terminate theincoming call to the mobile station, the network determines the callstate of the mobile station, as indicated by blocks 52 and 54. Inparticular, the network may determine whether the mobile station isbusy, as indicated by block 52. If the mobile station is not busy, thenthe network may page and alert the mobile station, as indicated by block56. The incoming call is then connected when the mobile station answers.If the mobile station is busy, then the network may determine whetherthe mobile station is “fully engaged,” as indicated by block 54.

[0032] As used herein, a mobile station is “fully engaged” when itcannot be connected to an incoming call without being disconnected froman existing call. Being disconnected from a call may be distinguishedfrom putting a call on hold or suspending the call, as is done with callwaiting. Once a call, e.g., a call involving two parties, isdisconnected, circuits or other resources are released. In order for theparties to be re-connected, typically a new call must be originated,such as by one of the parties dialing the other party's telephonenumber.

[0033] A mobile station may be fully engaged because it is using themaximum number of call legs allowed it, e.g., because of call waiting orthree-way calling. In some embodiments, a mobile station may be fullyengaged if it is engaged in a single active data session. In otherembodiments, an active data session may not be sufficient to fullyengage the mobile station; the mobile may instead be fully engaged if,for example, it is engaged in one active data session and one or morevoice calls.

[0034] If the mobile station is not fully engaged, then the network mayuse a call waiting procedure to allow the user to put an existing callon hold and connect the incoming call, as indicated by block 58. If themobile station is fully engaged, then the network transmits an incomingcall notification message to the mobile station, as indicated by block60.

[0035] In response to the incoming call notification, the mobile stationpreferably provides a user-discernible indication that the user may takean incoming call, as indicated by block 62. The user-discernibleindication may be visual. For example, the mobile station may displaytext, such as an incoming call notification message, and/or graphics onits screen, or the mobile station may light or flash an indicator light.Alternatively, or additionally, the mobile station may provide anaudible indication to the user, such as a click or a tone, or a tactileindication, such as a vibration. In a preferred embodiment, theuser-discernible indication includes an incoming call notificationmessage that identifies the caller, such as by name and/or telephonenumber.

[0036] Preferably, the user is then able to signal a desired manner ofhandling the incoming call. For example, the user may be able to signalthat the user wishes to drop existing calls and accept the incoming callby pressing a button on mobile station, such as the END button, bypressing a series of buttons, by interacting with a touch sensitivescreen, by speaking a voice command, or by interacting with mobilestation in some other fashion. The user may also be able to signal thatthe incoming call should be handled in some other fashion. For example,the user may have the option of sending the incoming call to a voicemail system or to another telephone number. When the user signals adesired manner of handling the incoming call, the mobile stationresponsively transmits the user's selection to the network.

[0037] The user-discernible indication provided by the mobile stationmay also indicate to the user the options available for handling theincoming call and may indicate how the user may choose each option. Forexample, the mobile station may display on its screen text that explainsthat the user may drop existing calls and take the incoming call bypressing a button, such as the END button. The text may also identifyother options available to the user and how the user may choose them.Alternatively, the user may be able to have the mobile station respondto some or all incoming call notifications in a predetermined, automaticfashion. For example, the user may be able to have the mobile stationautomatically ignore incoming call notifications from certain callers orautomatically accept calls in response to incoming call notificationsfrom certain callers.

[0038] The mobile station may be programmed with one or moremessage-handling applications that control the operation of the mobilestation in response to incoming call notifications. For example, themessage-handling application may display text or graphics on the screenor generate an audible indication in accordance with the informationprovided in the incoming call notification. The message-handlingapplication may also specify what the mobile station transmits inresponse to the incoming call handling options selected by the user.

[0039] After transmitting the incoming call notification, the networkdetermines whether the mobile station has transmitted a user selectionwithin the allotted time period, as indicated by block 64. If the mobilestation has not, indicating that the user has not chosen to accept theincoming call or to specify any other handling of the incoming call,then the network may handle the incoming call in a default manner, asindicated by block 66. Such default handling may, for example, includesending the incoming call to the mobile station user's voice mail.

[0040] If the mobile station has transmitted a user selection, thenetwork determines whether the user selection is an incoming callacceptance, as indicated by block 68. If the user selection is anincoming call acceptance, then the network drops one or more calls inwhich the mobile station is currently engaged and connects the incomingcall to the mobile station, as indicated by block 70. If the userselection specifies some other handling of the incoming call, such assending it to another telephone number, then the network handles theincoming call in accordance with the user selection, as indicated byblock 72.

[0041] The operations illustrated in FIG. 2 may be carried out inwireless telecommunications network 10 shown FIG. 1. FIG. 3 shows asimplified call flow for how this may be accomplished in an exemplaryembodiment. Thus, in the call flow of FIG. 3, it is assumed that mobilestation 14 is communicating with wireless telecommunications network 10over an air interface, as shown in FIG. 1.

[0042] The process begins when a caller initiates a call to mobilestation 14, such as by dialing a directory number corresponding tomobile station 14. The caller may be using a landline telephony device,such as telephone 30, or a fax machine or a modem. Alternatively, thecaller may be using a mobile station, such as a wireless telephone,wireless PDA, or wirelessly equipped laptop computer. In other cases,the caller may be using some other type of device to call mobile station14. The call may reach PSTN 20 via a switching system, such as SSP 32 orhome MSC 28. Alternatively, the call may reach PSTN 20 via a gateway,such as may occur if the caller uses VoIP.

[0043] However the call is originated, in step 100 the call is routedfrom PSTN 20 to home MSC 28, the network element assigned to thedirectory number that the caller dialed. In an exemplary embodiment,step 100 may involve the exchange of SS7 ISUP signals.

[0044] In the example of FIGS. 1 and 3, mobile station 14 is roaming inthat it is operating outside of the area being served by home MSC 28. Asa result, home MSC 28 engages in signaling, such as IS-41 signaling, tolocate mobile station 14 and to route the call to mobile station 14.

[0045] For example, home MSC 28 may send to HLR 22 an IS-41 LOCREQinvoke identifying mobile station 14 as the called party, as shown instep 102. In response, HLR 22 determines that mobile station 14 is beingserved by serving MSC 18. Then, HLR 22 sends to serving MSC 18 an IS-41ROUTEREQ invoke identifying mobile station 14, as shown in step 104.

[0046] When serving MSC 18 receives the ROUTEREQ of step 104, itdetermines whether mobile station 14 is available to take the incomingcall. Specifically, if mobile station 14 is not engaged in any call,then serving MSC 18 may simply page and alert mobile station 14 to tryto connect the incoming call. If mobile station 14 is engaged in a callbut not fully engaged, then serving MSC 18 may use call waiting tonotify the user of the incoming call. In either case, serving MSC 18would typically respond to the ROUTEREQ with a temporary locationdirectory number (TLDN) that home MSC 28 may use to route the call toserving MSC 18.

[0047] In the case illustrated in FIG. 3, however, serving MSC 18determines that mobile station 14 is fully engaged. For example, MSC 18,like many commercially available MSC's, may have built-in software thatkeeps track of whether mobile stations it is serving, such as mobilestation 14, are fully engaged. As a result, mobile station 14 cannot beconnected to the incoming call without being disconnected from anexisting call. Moreover, because the mobile station is fully engaged,call waiting is not available to notify the user of the incoming call.Accordingly, serving MSC 18 sends to HLR 22 an IS-41 routereq returnresult that identifies mobile station 14 and indicates that it is busy,as shown in step 106. The routereq return result of step 106 may alsoindicate how mobile station 14 is busy. For example, the routereq returnresult of step 106 may indicate whether mobile station 14 is engaged invoice calls or in an active data session. In step 108, HLR 22 sends tohome MSC 28 a locreq return result indicating that mobile station 14 isbusy.

[0048] When home MSC 28 receives the locreq return result of step 108,indicating that mobile station 14 is busy, home MSC 28 may send to SCP24 an IS-771 T_BUSY invoke in order to receive instructions on how tohandle the incoming call, as shown in step 110. The T_BUSY invoke ofstep 110 identifies the caller and mobile station 14, and it indicatesthat mobile station 14 is busy. If the routereq return result that homeMSC 28 received in step 108 indicated how mobile station 14 was busy,then the T_BUSY invoke of step 110 may also include this information. Ofcourse, in the case mobile station 14 is not roaming but insteadoperating in the area served by home MSC 28, then home MSC 28 may send aT_BUSY invoke to SCP 24 without first sending a LOCREQ invoke to HLR 22.

[0049] When SCP 24 receives the T_BUSY invoke of step 110, SCP 24 mayobtain a service profile corresponding to mobile station 14 and may alsoexecute service logic to determine how to respond. The service profilemay indicate whether the user of mobile station 14 subscribes to theincoming call notification service of the present invention; it may alsoinclude parameters specifying under what conditions mobile station 14should receive an incoming call notification and how it should be sent.For example, the user may wish to receive an incoming call notificationfrom only certain callers.

[0050] SCP 24 may also query one or more network elements to determinehow to provide the incoming call notification. In a preferredembodiment, before transmitting the incoming call notification SCP 24first determines how mobile station 14 is fully engaged, e.g., whethermobile station 14 fully engaged by voice calls or by an active datasession. SCP 24 may make this determination by sending a call statequery identifying mobile station 14 to call state server 48, as shown instep 112. In response, call state server 48 may send to SCP 24 a callstate response that specifies how mobile station 14 is fully engaged, asshown in step 114. For example, the call state response may specifywhether the mobile station 14 is engaged in voice calls or in an activedata session. If mobile station 14 is engaged in an active data session,the call state response may also indicate what type of data session. Forexample, the call state response may indicate whether mobile station 14is engaged in a data session that is sensitive to delay associated withsending the incoming call notification to mobile station 14. Suchdelay-sensitive data sessions may include real-time media sessions, suchas VoIP teleconferencing. Other activities, such as web browsing ore-mail retrieval may not be as sensitive to delays caused by theincoming call notification.

[0051] SCP 24 then formulates an incoming call notification. In manycases, the incoming call notification may be transmitted to mobilestation 14. In other cases, however, the incoming call notification maybe transmitted to an alternate device associated with the user of mobilestation 14, such as a pager, a PDA, a laptop computer, or a desktopcomputer, with or without a wireless connection. As described in moredetail below, the user's service profile and service logic executed bySCP 24 may determine where the incoming call notification should besent.

[0052] A number of different approaches exist for providing thisincoming call notification. One approach is to use short message service(SMS) messages, such as those defined in IS-637 specifications. Thisapproach is preferred when the mobile station is engaged in one or morevoice calls. Another approach is to use packet protocol messages, suchas session initiation protocol (SIP) messages or wireless applicationprotocol (WAP) push messages. This approach is preferred when the mobilestation is engaged in an active data session.

[0053] SCP 24 may formulate the incoming call notification based on theinformation provided in the call state response of step 114. Forexample, if the call state response indicates that mobile station 14 isfully engaged in voice calls then SCP 24 may formulate the incoming callnotification as an SMS message. If the call state response indicatesthat mobile station 14 is engaged in an active data session, then SCP 24may formulate the incoming call notification as a SIP message or otherpacket protocol message. SCP 24 may also use the information from thecall state response of step 114 to determine whether to send theincoming call notification to mobile station 14 or to some otherdestination. For example, if the call state response indicates thatmobile station 14 is engaged in an active data session that may bedelay-sensitive, then SCP 24 may send the incoming call notification toan alternate destination instead of to mobile station 14. The alternatedestination may be a pager, a PDA, a computer, or other deviceassociated with the user of mobile station 14.

[0054] SCP 24 may also consult the user's service profile to determinehow to send the incoming call notification. For example, the user maywant to receive only SMS messages, or only packet protocol messages. Theservice profile may also specify that the incoming call notificationmay, at least under certain conditions, be sent to an alternatedestination.

[0055] SCP 24 may also maintain call history information regarding howthe user has made use of the incoming call notification service in thepast. SCP 24 may then consult the user's call history information todetermine how to instruct home MSC 28. For example, if the user has beenignoring a certain number of incoming call notifications within acertain period of time, the SCP 24 may instruct home MSC 28 to handlethe call in a default fashion, such as sending it to voice mail, ratherthan send another incoming call notification to mobile station 14.

[0056] Whatever form the incoming call notification takes, it preferablyincludes the information needed to provide the desired user-discernibleindication by mobile station 14. For example, if the user-discernibleindication includes the calling party's telephone number, then SCP 24may formulate the incoming call notification so as to include thecalling party's telephone number from the T_BUSY invoke of step 110. SCP24 may also include in the incoming call notification other text to bedisplayed, such as an explanation to the user on how to take theincoming call. Alternatively, this and other elements of theuser-discernible indication that are not dependent on the specifics ofthe incoming call may be specified by the message handling applicationin mobile station 14, rather than by the incoming call notification.

[0057] After SCP 24 formulates the incoming call notification, SCP 24may transmit it to mobile station 14, as shown in step 116. Although,for the sake of simplicity, FIG. 3 shows SCP 24 transmitting theincoming call notification to mobile station 14 directly in step 116,the incoming call notification may actually be transmitted to mobilestation 14 in several steps involving several network elements.Moreover, the details of how the incoming call notification reachesmobile station 14 may depend on the type of message used.

[0058] To send the incoming call notification as an SMS message, SCP 24may first send to HLR 22 an IS-771 SEARCH invoke identifying mobilestation 14, and HLR 22 may respond with the MSC ID of the MSC currentlyserving mobile station 14, i.e., serving MSC 18. SCP 24 may then send anSMDPP message, containing the text to be displayed on the mobilestation, to serving MSC 18. This point-to-point transmissionadvantageously bypasses the message center (MC) that is normally used todeliver SMS messages, so that the incoming call notification messagewill be delivered to the mobile station in real time. Serving MSC 18, inturn, transmits the text, as an SMS message, to mobile station 14, via apaging channel.

[0059] To send the incoming call notification using SIP, SCP 24 may senda SIP request to SIP proxy server 46 addressed to a mobile directorynumber corresponding to mobile station 14. In a preferred embodiment,the SIP request is of the MESSAGE method type and contains text to bedisplayed by mobile station 14. Other SIP methods, such as INVITE, couldalso be used. SIP proxy server 46, in turn, forwards the SIP request toPDSN 38, either directly or via one or more other SIP proxy servers. Tolocate PDSN 38 as the node serving mobile station 14, these SIP proxyservers may query one or more location servers or other databases. OncePDSN 38 receives the SIP request, it forwards it to BSC/PCF 16, and BTS12 transmits it over an air interface to mobile station 14.

[0060] Alternatively, instead of querying call state server 48, SCP 24may use other means to determine how to send the incoming callnotification. For example, the T_BUSY invoke of step 110 may indicatewhether mobile station 14 is busy in voice calls or an active datasession. Alternatively, SCP 24 may simply send either an SMS message ora packet protocol message, or both, without determining how mobilestation 14 is fully engaged.

[0061] In addition to formulating and transmitting the incoming callnotification, SCP 24 sends home MSC 28 an IS-771 t_busy return result,as shown in step 118, in order to instruct home MSC 28 how to handle theincoming call. The t_busy return result of step 118 preferably instructshome MSC 28 to play an announcement to the caller, as shown in step 120.The announcement to the caller may be used to take up the time allottedfor the user of mobile station 14 to decide whether to take the incomingcall. Thus, the announcement may, for example, ask the caller to bepatient because the call may take some time to go through.

[0062] The t_busy return result of step 118 may also instruct home MSC28 to make another attempt to terminate the incoming call after playingthe announcement of step 120. The purpose of this second terminationattempt is to connect the incoming call to mobile station 14, in theevent the user has, in the time allotted, accepted the incoming call inresponse to the incoming call notification, as described in more detailbelow.

[0063] Once mobile station 14 receives the incoming call notification ofstep 116, mobile station 14 preferably provides the user-discernibleindication, as described above. If the user chooses one of the availableoptions within the time allotted, mobile station 14 responsivelytransmits a signal indicating the user selection, as shown in step 122.In the example illustrated in FIG. 3, the user has chosen to take theincoming call, so the user selection of step 122 is an incoming callacceptance.

[0064] If the response to the incoming call acceptance of step 122 is anincoming call acceptance, serving MSC 18 drops one or more of the callsin which mobile station 14 is engaged so that the incoming call may beconnected to mobile station 14. Thus, if mobile station 14 is engaged inan active data session, then serving MSC 18 may drop the data session.If mobile station 14 is engaged in voice calls, then serving MSC 18 maydrop one or more of the call legs that mobile station 14 is using.

[0065] During the period of time allotted for the user to accept theincoming call, home MSC 28 plays the announcement of step 120. When theannouncement of step 120 is completed, home MSC 28 sends another LOCREQinvoke to HLR 22, as shown in step 124, in accordance with theinstructions provided by the t_busy return result of step 118. HLR 22,in turn, responsively sends another ROUTEREQ invoke to serving MSC 18,as shown in step 126.

[0066] However, in the example of FIG. 3 the user has accepted theincoming call within the allotted time period. As a result, when servingMSC 18 receives the ROUTEREQ of step 126, serving MSC 18 will havedropped one or more calls such that mobile station 14 is no longer fullyengaged. Accordingly, in response to the ROUTEREQ of step 118, servingMSC sends back to HLR 22 a routereq return result containing a TLDN, asshown in step 128. HLR 22, in turns, sends to home MSC 28 a locreqreturn result containing the TLDN, as shown in step 130. Using thisTLDN, home MSC 28 routes the incoming call to serving MSC 18 byexchanging SS7 ISUP messages, as shown in step 132. Once the incomingcall is routed to serving MSC 18, serving MSC 18 pages and alerts mobilestation 14, as shown in step 134.

[0067] If the user does not accept the incoming call within the allottedtime period, then mobile station 14 will still be fully engaged. Thus,in response to the ROUTEREQ of step 118, serving MSC 118 may respondwith a routereq return result that, once again, indicates mobile station14 is busy. When the busy indication reaches home MSC 28, home MSC 28may send SCP 24 a T_BUSY invoke, as before.

[0068] This time, however, SCP 24 may respond differently. Specifically,the service logic that SCP 24 uses to process the T_BUSY invoke mayprovide for alternate handling of the incoming call if SCP 24 receivestwo T_BUSY invokes involving the same telephone numbers within a certainperiod of time. For example, in response to the second T_BUSY invoke,SCP 24 may instruct home MSC 28 to send the incoming call to analternate location or number, such as a voice mail system, or aninteractive voice response (IVR) system, or to take some other alternateaction.

[0069]FIG. 4 illustrates an exemplary call flow for the case where theuser selection in response to the incoming call notification is otherthan an incoming call acceptance. For example, the user selection may beto forward the incoming call to a voice mail system or to anothertelephone number or to handle the incoming all in some other fashion.

[0070] In the example of FIG. 4, the call flow may be similar to theexample of FIG. 3 up to the point where the user has selected a responseto the incoming call notification and mobile station 14 has transmittedthe user selection, as shown in step 200. The user selection of step 200is preferably a message that is sent to SCP 24. For example, the userselection may be transmitted as a SIP message, as a mobile-originatedSMS message, or as some other message.

[0071] When home MSC 28 is finished playing the announcement of step120, it transmits a LOCREQ invoke to HLR 22, shown in step 202, inaccordance with the instructions of the t_busy return result of step118. HLR 22 responsively sends a ROUTEREQ invoke to serving MSC 18, asshown in step 204. In this example, however, the user has not simplyaccepted the incoming call, so mobile station 14 is still fully engaged.Accordingly, serving MSC 18 once again sends back to HLR 22 a routereqreturn result indicating that mobile station 14 is still busy, as shownin step 206. HLR 22 forwards the busy indication to home MSC 28 in alocreq return result, as shown in step 208.

[0072] In response to the busy indication, home MSC 28 again sends SCP24 a T_BUSY invoke, as shown in step 210. By this time however, SCP 24has received the user selection of step 200. Thus, in response to theT_BUSY of step 210, SCP 24 sends home MSC 28 a t_busy return result instep 212 that instructs home MSC 28 how to handle the incoming call inaccordance with the user selection.

[0073] 3. Call State Server

[0074] As noted above, wireless telecommunications system 10 may includea call state server 48 that keeps track of the call state of mobilestations, such as mobile station 14. The call state information mayspecify whether a given mobile station is: (1) not busy; (2) busy on onevoice call; (3) busy on two or more voice calls; or (4) busy on anactive data session. In cases (2) and (3), the mobile station is fullyengaged. With respect to case (3), a mobile station may, for example, bebusy on two or more voice calls because it is using call waiting to beconnected to two or more calls or because it is using two or more calllegs for a conference call, such as three-way calling. With respect tocase (4) the mobile station may be engaged in an active data session viaBSC/PCF 16 and PDSN 38, a “3G” data session, or via serving MSC 18 andIWF 44, a “2G” or CSD data session. In case (4), call state server 48may also specify the type of data session, such as web browsing or VoIP.

[0075] SCP 24 may keep track of the number of voice calls mobile station14 is engaged in and may provide this information to call state server48. For example, serving MSC 18 may be provisioned with triggers thatcause it to signal SCP 24 whenever a mobile station that it is serving,such as mobile station 14, originates a call, answers a call, or ends acall. In this way, SCP 24 will know when mobile station 14 is engaged invoice calls. SCP 24 may push this information to call state server 48 atappropriate times, such as whenever a change in the call state of mobilestate 14 occurs. Alternatively, call state server 48 may query SCP 24 toobtain the call state information.

[0076] Call state server 48 may determine whether mobile station 14 isengaged in an active data session in a number of different ways. In oneapproach, BSC/PCF 16 may keep track of the state of the data session,i.e., whether active or dormant. Thus, BSC/PCF 16 may push thisinformation to call state server 48 at appropriate times, such as when achange occurs.

[0077] In another approach, PDSN 38 may, in accordance with the RADIUSaccounting protocol, send AAA server 42 a START message when it startsservice delivery to mobile station 14 and a STOP message when it stopsservice delivery. Moreover, each STOP message may include a flagindicating whether the data session is being continued, i.e., whetherthe data session has been torn down or is simply dormant. Thus, AAAserver 42 may push the information from the START and STOP messages tocall state server 48, or call state server 48 may query AAA server 42 toobtain the information. Further details regarding this approach aredescribed in the U.S. Patent Application, identified as Sprint DocketNo. 1952 and titled “Method and System for Network PresenceNotification,” which is filed concurrently herewith and which is fullyincorporated herein by reference.

[0078] For CSD sessions, either serving MSC 18 or IWF 44 could push thesession status to call state server 48. For CSD sessions, theretypically is no distinction between active and dormant data sessions.The session status may simply be whether mobile station 14 is connectedto packet-switched network 34 in a CSD session via IWF 44.

[0079] Call state server 48 may also maintain information about the typeof data session mobile station 14 is engaged in from the one or moreapplication servers 36 involved in the session. For example, if mobilestation 14 is engaged in a VoIP teleconferencing session, then ateleconferencing server involved in the session may push thisinformation to call state server 48.

[0080] 4. Conclusion

[0081] In exemplary embodiments, the user of a mobile station that isfully engaged, i.e., a mobile that is involved in one or more existingcalls and cannot be connected to an incoming call without beingdisconnected from one of the existing calls, may, nonetheless, benotified of an incoming call. The user may also be able to signal themobile station to drop one or more of the existing calls and take theincoming call. Even if the user does not take the incoming call, theincoming call notification may identify the caller, so that the user maycall the caller back at a convenient time. Advantageously, the wirelesstelecommunications network may provide this incoming call notificationservice without placing large additional demands on its resources. Incontrast, with call waiting when the user accepts an incoming call, theexisting calls are placed on hold or suspended, rather thandisconnected, thereby tying up network resources.

[0082] Exemplary embodiments of the present invention have beendescribed above. Those skilled in the art will understand, however, thatchanges and modifications may be made to these embodiments withoutdeparting from the true scope and spirit of the invention, which isdefined by the claims.

What is claimed is:
 1. A method of incoming call notification for amobile station, said mobile station being connected to at least one callover an air interface, said method comprising: detecting a request toconnect an incoming call to said mobile station; determining whethersaid mobile station is fully engaged such that said mobile stationcannot be connected to said incoming call without being disconnectedfrom at least one of said at least one call; and if said mobile stationis fully engaged, transmitting an incoming call notification to saidmobile station.
 2. The method of claim 1, further comprising: inresponse to said incoming call notification, said mobile stationproviding a user-discernible indication.
 3. The method of claim 2,wherein providing a user-discernible indication includes said mobilestation visibly displaying an incoming call notification message.
 4. Themethod of claim 3, wherein said incoming call notification messageidentifies said incoming call.
 5. The method of claim 4, wherein saidincoming call notification message includes text identifying a callingparty of said incoming call.
 6. The method of claim 5, wherein said textincludes a telephone number of said calling party.
 7. The method ofclaim 1, further comprising: receiving an incoming call acceptance fromsaid mobile station; and in response to said incoming call acceptance,disconnecting at least one of said at least one call and connecting saidincoming call.
 8. The method of claim 1, wherein said at least one callincludes a voice call.
 9. The method of claim 8, wherein transmitting anincoming call notification to said mobile station includes transmittinga short message service (SMS) message to said mobile station.
 10. Themethod of claim 1, wherein said at least one call includes an activedata session.
 11. The method of claim 10, wherein transmitting anincoming call notification to said mobile station includes transmittinga packet protocol message to said mobile station.
 12. The method ofclaim 11, wherein said packet protocol message is a session initiationprotocol (SIP) message.
 13. The method of claim 12, further comprising:receiving an incoming call acceptance from said mobile station; and inresponse to said incoming call acceptance, disconnecting said activedata session and connecting said incoming call.
 14. The method of claim1, wherein said at least one call includes a first voice call and asecond voice call.
 15. The method of claim 14, further comprising:receiving an incoming call acceptance from said mobile station; and inresponse to said incoming call acceptance, disconnecting said firstvoice call and said second voice call and connecting said incoming call.16. The method of claim 1, wherein said at least one call includes avoice call and an active data session.
 17. The method of claim 1,further comprising: detecting whether said mobile station is engaged inan active data session; if said mobile station is engaged in an activedata session, transmitting said incoming call notification to saidmobile station as a packet protocol message; and if said mobile stationis not engaged in an active data session, transmitting said incomingcall notification to said mobile station as a short message service(SMS) message.
 18. The method of claim 17, wherein said packet protocolmessage is a session initiation protocol (SIP) message.
 19. The methodof claim 1, wherein transmitting an incoming call notification to saidmobile station includes transmitting a short message service (SMS)message to said mobile and transmitting a packet protocol message tosaid mobile station.
 19. The method of claim 18, wherein said packetprotocol message is a session initiation protocol (SIP) message.
 21. Asystem for notifying a mobile station of an incoming call, said systemcomprising: a call connection system for connecting calls to said mobilestation over an air interface; and a call control system for controllingsaid call connection system, said call control system running servicelogic for formulating an incoming call notification to said mobilestation when said mobile station is fully engaged.
 22. The system ofclaim 21, wherein said call connection system includes a mobileswitching center (MSC).
 23. The system of claim 21, wherein said callconnection system includes a base station controller (BSC).
 24. Thesystem of claim 21, wherein said call connection system includes apacket data service node (PDSN).
 25. The system of claim 21, whereinsaid call control system includes a service control point (SCP).
 26. Thesystem of claim 21, wherein said incoming call notification message is ashort message service (SMS) message.
 27. The system of claim 21, whereinsaid incoming call notification message is a packet protocol message.28. The system of claim 27, wherein said packet protocol message is asession initiation protocol (SIP) message.
 29. The system of claim 21,further comprising: a call state server for maintaining call stateinformation for said mobile station, said call state server beingaccessible by said call control system.
 30. The system of claim 29,wherein said call state information indicates whether said mobilestation is engaged in an active data session.
 31. The system of claim30, wherein said call state information indicates a type of said activedata session.
 32. The system of claim 29, wherein said call stateinformation indicates whether said mobile station is engaged in a voicecall.
 33. A method of handling an incoming call for a mobile station,said mobile station being connected to at least one call over an airinterface, said mobile station being associated with a user, said methodcomprising: making a first attempt to connect an incoming call from acalling party to said mobile station; determining that said firstattempt is unsuccessful; in response to said unsuccessful first attempt,transmitting an incoming call notification; and making a second attemptto connect said incoming call from said calling party to said mobilestation.
 34. The method of claim 33, wherein said incoming callnotification is transmitted to said mobile station.
 35. The method ofclaim 33, wherein said incoming call notification is transmitted to analternate device associated with said user.
 36. The method of claim 33,further comprising: obtaining call state information for said mobilestation.
 37. The method of claim 36, further comprising: selecting adestination based on said call station information, wherein saidincoming call notification is transmitted to said destination.
 38. Themethod of claim 37, wherein said incoming call notification istransmitted to an alternate device associated with said user, if saidmobile station is engaged in a delay-sensitive data session.
 39. Themethod of claim 33, further comprising: obtaining call historyinformation for said mobile station; and determining whether to transmitsaid incoming call notification based on said call history information.40. The method of claim 33, further comprising: receiving an incomingcall acceptance from said mobile station; in response to said incomingcall acceptance, disconnecting at least one of said at least one call;and as a result of said second attempt, connecting said incoming call.41. The method of claim 33, further comprising: in response to saidunsuccessful first attempt, playing an announcement to said callingparty.
 42. The method of claim 33, wherein said at least one callincludes a voice call.
 43. The method of claim 42, wherein transmittingan incoming call notification to said mobile station includestransmitting a short message service (SMS) message to said mobilestation.
 44. The method of claim 33, wherein said at least one callincludes an active data session.
 45. The method of claim 44, whereintransmitting an incoming call notification to said mobile stationincludes transmitting a packet protocol message to said mobile station.46. The method of claim 45, wherein said packet protocol message is asession initiation protocol (SIP) message.
 47. The method of claim 33,wherein said at least one call includes a voice call and an active datasession.